Galapagos Islands, Ecuador. – The famed Galapagos finches, the birds that helped to inspire Charles Darwin’s theory of evolution, the backbone of all natural sciences, are in peril. Not by the hands of man, or giant land turtles, or the prehistoric-looking iguanas that share the islands, but by parasitic flies.

Parasitic flies, lay eggs in the nests of the finches, and their developing larvae kill finch nestlings before they fledge. The parasitic flies were accidentally introduced to the remote Galapagos Islands, located off the Pacific Coast of Ecuador, South America, and ornithologists are gravely concerned for the islands’ 13 diverse species of small, highly adapted finches.

Darwin’s Finches are best known for the diversity of bill shapes they have developed, each with a special function for feeding. Some species have large, strong bills used for cracking seeds. Others have slim, pointed bills for catching and feeding on insects, others have slimmer bills to feed on flower nectar, and at least one particular species is one of the only birds known to use tools. This finch is adept at breaking off a cactus spine and using it to extract insects and insect larvae from holes in wood or vegetation.

This diversity of finch species with different sizes and body and bill forms, along with their different feeding strategies and habitat use, helped Charles Darwin to formulate his theories of adaptation and natural selection as they affect evolution. Darwin visited the remote archipelago in 183x during his ‘round the world voyage aboard the Beagle.

Alarm for Darwin’s finches was sounded after ornithologists monitored the nesting success of 12 species of birds on the Galapagos, including 7 or the 13 finch species. The scientists, Dr. Birgit Fessl and Dr. Sabine Tebbich from Austria’s Konrad Lorenz Institute, found that virtually all broods were blighted by parasitic fly larvae.

The nesting success of many of these birds is being impacted dramatically, and could signal the extinction of some species.

Dr. Fessl told BBC News that “This is a very big problem. If it was just the parasites, maybe the birds could cope. But there is a combination of factors including losses because of very dry years in the Galapagos and predation of nests by [introduced] rats.” The combination of these factors is having a dire effect on populations of birds, and Fissl believes that some species could be pressed to extinction without assistance.

The most obvious candidate for extinction is the Mangrove Finch, which is known to number only about 110 individuals, according to Dr. Nigel Collar from BirdLife International and author of the book, Threatened Birds of the Americas.

Both Collar and Fissl emphasized the importance of continued and expanded studies of the nesting attempts of Galapagos finches and other passerine birds. To date, the Mangrove Finches have not been studies, but Dr. Fissl noted that there is no reason to believe they have not been affected by the parasitic flies because the insects are not host-specific and appear to attack nest of any small birds they come in contact with
Actually, no less than 3 species of parasitic flies were accidentally introduced to the Galapagos Islands, the first of which was found in 1997.

On the large island of Santa Cruz, Dr Fessl and Dr. Tebbich found an extremely high rate of infestation of finch nests – 97 percent! Each finch nestling had an average of 23 fly larvae on it, and more than 25 percent of the nestlings were dying, apparently in reaction to the affect of the insects.

What can be done to help the beleaguered Darwin finches?

There is hope, although it would take a committed effort to combat the effects of the parasitic flies on the finches.

Dr. Fissl explained that it may be possible to sterilize active bird nests. They tried disinfecting the nest with an insecticide during the early nestling phase. The researchers took the small, helpless nestlings out of the nest for a couple minutes while they disinfected the nest with an insecticide. The process reduced the parasite numbers in the nest by 80 to 90 percent.

Stating that the process takes a lot of work, it is a possibility that can be used to save the Mangrove Finches and other highly affected species from extinction.

Original story, “Darwin's Finches at Risk,” by John Amos from BBC News Online:
http://news.bbc.co.uk/go/em/fr/-/2/hi/science/nature/2415261.stm